A microarray collectively represents a material or technology in which a plurality of objects of inspection and experiment are fixed, and inspection and experiment are performed at a time. Particularly, development focused on a DNA microarray using a nucleic acid has processed in fields of biology, medicine, and pharmacy from the end of 20th century, and the DNA microarray has been used.
For example, when using DNA microarray, mRNA is extracted from a sample, cDNA that is synthesized by inverse transcription is biotin labeled, and hybridization with DNA on a substrate of the DNA microarray is performed. In addition, a sample formed by the hybridization is irradiated with excitation light, the intensity of fluorescence that is emitted from a fluorescent substance contained in the sample is detected by a fluorescence microscope, a fluorescence laser scanner, and the like. An expression level of mRNA can be determined on the basis of the intensity of fluorescence that is detected.
A fluorescence detection device, which irradiates a sample disposed in a microarray with excitation light and detects fluorescence from the sample, is typically classified into two types including a coaxial vertical type and a non-coaxial vertical type. In the coaxial vertical type, excitation light is allowed to pass through a condensing lens provided on an optical path of the excitation light and a sample is irradiated with the excitation light. In addition, fluorescence from the sample excited by the excitation light is condensed by the same condensing lens and is focused on an imaging device.
In the coaxial vertical type, a device background rises due to intrinsic fluorescence of the condensing lens, which is generated when the excitation light passes through the condensing lens, and thus it is difficult to accurately detect weak fluorescence from the sample.
Therefore, as a device that improves the detect of the coaxial vertical type, a non-coaxial vertical type as disclosed in Patent Document 1 is known. In the device disclosed in Patent Document 1, a sample is irradiated with excitation light from an oblique lower side, and fluorescence from the sample is condensed by a lens disposed on a lower side of the sample in order for the lens not to overlap with the optical axis of the excitation light. In this device, the excitation light does not pass through the lens, and thus the intrinsic fluorescence of the lens is prevented from being generated.